1. Field of the Invention
The present invention relates to a reflection-type liquid crystal display panel and a method of fabricating the same. More particularly, the present invention relates to a reflection-type liquid crystal display panel suitable for use as a display unit for OA apparatus including note-size lap top personal computers and word processors, video apparatus including pocketable television sets, and game machines, and a method of fabricating the same.
2. Description of the Related Art
The application of liquid crystal display panels to pocketable liquid crystal television sets, lap top personal computers and word processors has rapidly developed in recent years. Particularly, reflection-type liquid crystal displays, which reflect incident external light to display images, are being watched with keen interest because reflection-type liquid crystal display panels do not need any backlight unit, are capable of operating at a low power consumption rate and of being powered by batteries; and are thin and of lightweight.
Generally known reflection-type liquid crystal display panels are TN liquid crystal display panels in which a liquid crystal is driven in a twisted nematic (TN) mode, and STN liquid crystal display panels in which a liquid crystal is driven in a super twisted nematic (STN) mode. The TN liquid crystal display panel displays monochromatic images by using the optical properties of a liquid crystal display panel, namely, an optically rotatory characteristic which is exhibited when no voltage is applied thereto and a polarization canceling characteristic which is exhibited when a voltage is applied thereto.
A dichromatic dye is added to a known amorphous chiral nematic guest-host liquid crystal, and the orientation of the liquid crystal is controlled by voltage to control the orientation of the dichromatic dye for displaying images. A liquid crystal display panel employing such a mixture of an amorphous chiral nematic guest-host liquid crystal and a dichromatic dye does not need any polarizing plate, and has a high luminance and a wide viewing angle.
A color liquid crystal display has a liquid crystal display panel provided with an R-, a G- and a B-filter therein, and displays multicolor or full-color images by utilizing an optical switching characteristic. Currently, TN reflection-type liquid crystal display panels are employed in portable liquid crystal television sets, namely, pocketable liquid crystal television sets, driven in an active matrix driving mode or a passive matrix driving mode.
Referring to FIG. 14 showing a conventional monochromatic reflection-type liquid crystal display panel 20 in a typical sectional view, the liquid crystal display panel 20 has a back glass substrate 20a, a front glass substrate 20b disposed opposite to the back glass substrate 20a, an insulating layer 22 formed on the inner surface of the back glass substrate 20a, first electrodes 23a for forming pixels, formed on the insulating layer 22 in the pattern of stripes, an alignment film 24a formed on the insulating layer 22 so as to cover the first electrodes 23a, second electrodes 23b formed on the inner surface of the front glass substrate 20b in the pattern of stripes so as to extend perpendicularly to the first electrodes 23a, and an alignment film 24b formed on the inner surface of the front glass substrate 20b so as to cover the second electrodes 23b. The second electrodes 23b formed on the front glass substrate 20b are transparent electrodes, and the first electrodes 23a formed on the back glass substrate 20a are reflective electrodes of a conductive metal. The electrodes 23a and 23b of the glass substrates 20a and 20b are scanned in a passive matrix driving mode to display images on the liquid crystal display panel.
Referring to FIG. 15 showing a conventional monochromatic reflection-type liquid crystal display panel 20 in a typical sectional view, the liquid crystal display panel 20 has a back glass substrate 20a, a front glass substrate 20b disposed opposite to the back glass substrate 20a, an insulating layer 22 formed on the inner surface of the back glass substrate 20a, thin-film transistors (TFTs) 21 forming pixels and formed on the insulting layer 22, a matrix of electrodes 23a formed on the insulating layer 22, an alignment film 24a covering the TFTs and the electrodes 23a, a planar common electrode 23b formed on the inner surface of the front glass substrate 20b, and an alignment film 24b formed on the common electrode 23b. The common electrode 23b formed on the front glass substrate 20b is a transparent electrode, and the electrodes 23a formed on the back glass substrate 20a are reflective electrodes of a conductive metal.
The back glass substrate 20a and the front glass substrate are spaced a predetermined distance apart by a spacer, not shown, so as to form a space therebetween, and a liquid crystal, such as a guest-host liquid crystal, is filled in the space between the glass substrates 20a and 20b to form a liquid crystal layer 25, and the liquid crystal layer 25 is sealed in the space by a sealing member 26 attached to the peripheral parts of the glass substrates 20a and 20b.
The conventional reflection-type liquid crystal display panel is provided on its back surface with a reflecting plate of a metal, such as an aluminum plate, having a surface finished by grinding to provide the same with a light scattering property or a reflecting plate formed by depositing a metal, such as aluminum, by evaporation on a roughened surface of a base plate to provide the roughened surface with a light scattering property to secure a wide visual angle. Usually, the reflecting plate attached to the back surface of the liquid crystal display panel is omitted if reflective electrodes are employed. The reflection-type liquid crystal display panels 20 shown in FIGS. 14 and 15 are not provided with any reflecting plate on their back surfaces.
The foregoing conventional reflection-type liquid crystal display panel provided with the reflective electrodes having mirror surfaces reflects images of matters in front of the reflection-type liquid crystal display panel in a specular reflection mode and thereby the visibility of the screen of the reflection-type liquid crystal display panel is deteriorated.